1. Field of the Invention
The present invention relates to a vaporized fuel processing device provided on a path through which a fuel tank and a canister communicate with each other, and a vehicle with the vaporized fuel processing device. Particularly, it relates to a vaporized fuel processing device and a vehicle with the same in which a diaphragm valve unit opened at the time of increasing the pressure in a fuel tank is provided in a space inside a casing and in which a vent passage is provided to communicate with the space to improve the degree of freedom in selecting an installation position of the vent passage.
2. Description of the Related Art
An automobile or the like is provided with a fuel tank for reserving fuel to be supplied to a combustion chamber of an engine. The fuel tank has a vent system provided to allow air to come in and go out according to increase/decrease in fuel amount in the tank. The vent system is a system through which the inside of the fuel tank and a canister communicate with each other. In the case where the fuel tank is overcharged, the canister is disabled from being used because the canister is wetted with over flow fuel delivered to the canister. Therefore, a vaporized fuel processing device is provided on the top of the fuel tank so that the vent system can be interrupted to prevent air and fuel from being delivered to the canister when the tank is filled up.
Such a vaporized fuel processing device according to the related art is shown in FIGS. 5 and 6. A vaporized fuel processing device 1 is provided on the top of a fuel tank 2. A vent passage 14 is provided for connecting the vaporized fuel processing device 1 to a canister 5 for adsorbing fuel vapor. When the pressure of fuel vapor produced in the fuel tank 2 reaches a predetermined value at the time of refueling, a diaphragm valve 9 of a diaphragm valve unit 8 is opened because of a pressure difference. As a result, the fuel vapor flows into the canister 5 through the vent passage 14, so that the fuel vapor is adsorbed into an adsorbing agent in the canister 5 so as to be temporarily adsorptively reserved in the canister 5. When the internal combustion engine then revolves, the fuel vapor adsorbed into the canister 5, as well as atmospheric air taken in through an air intake pipe 6 attached to the canister 5, is sucked in on the basis of the negative pressure of a suction pipe not shown, and delivered from a vapor outlet pipe 7 to a cylinder of the internal combustion engine through the suction pipe.
The operation of the vaporized fuel processing device 1 according to the related art at the time of refueling will be described with reference to FIG. 6. When refueling starts in the condition that a filler cap 4 is opened, atmospheric air is fed to a back pressure chamber 11 of the diaphragm valve unit 8 through a pipe 13 opening into a feed pipe 3. The pressure in the fuel tank 2 increases as a result of refueling. The diaphragm valve 9 of the diaphragm valve unit 8 is opened upward from a second valve seat 16 on the basis of a pressure difference due to increase in the pressure in the fuel tank 2. Fuel vapor flows into the canister 5 through the vent passage 14 and is reserved in the canister 5. For this reason, the fuel vapor is prevented from being released from the feed pipe 3 to the atmospheric air.
A valve body 17 is formed on a top surface of a float 12 of the vaporized fuel processing device 1. When the float 12 moves up, the valve body 17 eventually abuts on a first valve seat 15 disposed above the float 12. Specifically, as refueling continues through the feed pipe 3, the liquid level of fuel in the fuel tank 2 rises. When the liquid level of fuel reaches the float 12, the fuel pushes the float 12 up. When the liquid level of fuel reaches a predetermined position, the valve body 17 on the top surface of the float 12 abuts on the first valve seat 15. Because the vent passage 14 is blocked when the valve body 17 abuts on the first valve seat 15, the pressure in the fuel tank 2 increases further to cause the refueling to stop automatically. On this occasion, the liquid level of fuel reaches a full-tank position (e.g., see Japanese Patent Laid-Open No. 37007/1999).
The vaporized fuel processing device shown in FIGS. 5 and 6, however, has the following problems. That is, in the vaporized fuel processing device according to the related art, the vent passage 14 is provided so as to communicate with an opening 18 which is provided with the second valve seat 16 and below the diaphragm valve 9 disposed horizontally. For this reason, the vent passage 14 must be inevitably extended horizontally, so that the vaporized fuel processing device lacks the degree of freedom in the layout for installation, for example, because the vaporized fuel processing device has to protrude from the top of the fuel tank.
Furthermore, since the surface area of the vaporized fuel processing device revealed from the top of the fuel tank is large, the shape of the vaporized fuel processing device is too poor to reduce the amount of hydrocarbon (hereinafter referred to as HC) transmitted from the fuel tank.
In addition, since the vent passage 14 must be inevitably extended horizontally, in the case where part of fuel in the fuel tank 2 leaks from the opening 18 into the vent passage 14 because of tilting etc. of a vehicle, the leakage fuel causes a harmful influence on the canister 5, thereby resulting in deterioration of the canister 5 due to the leakage fuel flowing up to the canister 5.